And in response to these developments in Ukraine, the United Nations today held another urgent meeting. Ukraine's ambassador wants to see Security Council members send a strong message to Russia to back off. But a U.N. envoy was unable to go to Crimea today. Russia is a permanent member of the Security Council and has veto power, so there doesn't seem to be much the Security Council can do. President Obama's national security team was also talking about how to respond. President Obama and President Putin did exchange a phone call today. Obama expressed a deep concern for what he called Russia's violation of Ukrainian sovereignty. The United States will suspend upcoming participation in preparatory meetings for the G-8.

NPR's Michele Kelemen joins us now to discuss these diplomatic efforts. Michele, President Obama has said there will be costs to Russia, but what is the U.S. considering?

MICHELE KELEMEN, BYLINE: Well, this is one of the problems. I mean, he didn't spell out what kind of costs there will be. And if you look, for instance, at U.S.-Russian trade relations, there's not much there, so it's hard to figure out, you know, what the U.S. could really do to make this costly to the Russians financially.

Europe, on the other hand, could cut back on its dependence on Russian energy, but it's not clear if the U.S. can persuade Europe to do that or help it fill the energy gaps if it does. And they also don't seem to be considering any sort of military show of force, at least not yet. As one defense official told us today, there's been no change to the U.S. military posture in Europe or the Mediterranean. The focus is on diplomacy.

That said, NATO announced a meeting of the North Atlantic Council tomorrow, on Sunday. Defense Secretary Chuck Hagel called his Russian counterpart. And as you mentioned, at the White House today, Hagel and other national security staff did meet to discuss the situation. We're told President Obama was not at that meeting.

RATH: And also on the diplomatic front, there's been some activity at the U.N. today. What's been going on there?

KELEMEN: Well, you know, they spent a good 45 minutes just talking about the format of the meeting, and Russia complained about that. Finally, they did decide to have an open session, which is, you know, a step up from the normal consultations. It was a chance to air concerns about what's happening. The deputy secretary general called for cool heads to prevail. Members of the council have a chance to raise their concerns.

And Ukraine's ambassador made a plea to all the countries to do whatever they can to stop, as he put it, the Russian aggression. He says there's still time. He was glad to hear that Secretary General Ban Ki-moon was trying to call Putin, even if Ban Ki-moon's envoy didn't make it into Crimea today as planned. The Ukrainian ambassador really urged everyone just to keep sending a message to Putin and supporting Ukraine's territorial integrity.

RATH: And in these discussions, the Ukrainians seem to be talking a lot about a 1994 agreement on non-interference. What's that about?

KELEMEN: It's called the Budapest memorandum. I mean, this was a time when Ukraine agreed to give up its nuclear weapons arsenal, these weapons that were left over from Soviet times. And at the time, the U.S., U.K., Russia and Ukraine got together, and they agreed to respect the territorial integrity of Ukraine - it was a non-interference pact, of course.

So the Ukrainians are bringing this up now hoping that the U.S., U.K. and others will do something to punish Russia for abrogating it. But it's not clear whether it will really force U.S., U.K. or anybody else's hands.